THURSDAY, June 20 (HealthDay News) -- Large doses of intravenous iron increase kidney dialysis patients' chances of developing a serious infection, but smaller doses given less frequently do not raise the risk, a new study shows.

Dialysis patients often develop anemia and must be given intravenous treatments of iron to correct the condition. Intravenous iron, however, can promote bacterial growth and weaken the immune system, putting patients at increased risk for infections.

This is the first large study to examine how different intravenous iron dosing regimens might affect this risk.

Researchers analyzed data from more than 117,000 dialysis patients who were followed for three months. Of these patients, 12 percent received a large amount of iron over a short period of time (bolus dosing); 49 percent received smaller, less frequent amounts of iron (maintenance dosing); and 38 percent received no iron.

Bolus dosing was associated with an increased risk of serious infection and infection-related death. There were 25 additional infections per 1,000 patient-years among patients who received bolus dosing, compared with those who received maintenance dosing.

These risks were particularly high among patients who used a catheter for dialysis (73 additional infections per 1,000 patient-years) and for those with a history of recent infection (57 additional infections per 1,000 patient-years).

Patients who received maintenance dosing did not have a greater risk of infection than those who received no iron, according to the study, which was published online June 20 in the Journal of the American Society of Nephrology.

"Although administration of iron is necessary to manage anemia in hemodialysis patients, our results suggest that providing a large amount of iron over a short time may increase the risk of serious infections in dialysis patients," study author Maurice Alan Brookhart, from the University of North Carolina at Chapel Hill, said in a journal news release. "Smaller, less frequent doses of iron appear to be safer."